Progressive burn shell

ABSTRACT

A shotgun shell designed to generate a lower and more extended pressure curve upon ignition of the powder. The shell consists of a conventional casing, primer and shot cup, the latter being made of any of a number of configurations and materials. Disposed intermediate the primer end and in covering relation to the powder is a pressure plate that conforms to the cross-sectional shape of the casing interior. The pressure plate, in preferred form, contains a plurality of apertures so that upon application of a specified relatively low pressure, the surface area of the plate which the apertures define is caused to fracture, thus reducing the pressure in the powder chamber of the casing. As a result, the increasing kinetic energy generated by the continued burning of the powder (which is normally utilized to &#39;&#39;&#39;&#39;initiate movement&#39;&#39;&#39;&#39; of the static shop cup) may be applied toward the &#39;&#39;&#39;&#39;acceleration&#39;&#39;&#39;&#39; of the shop cup since the initial movement of the cup will have been initiated by the low-pressure force occurring upon fracturing of the plate.

United States Patent 11 13,575,113

72] Inventors Clifford Logan Ashbrook FOREIGN PATENTS 5027 Chee 884,993 /1943 France 102/42 Wilson Gord n W g, 33 Rlvercrwt 213,242 9/1909 Germany 102/42 Dri Houston, 77042 732,633 6/1955 Great Britain 102/43 (P) [21 Appl. No. 708,223 [22] Filed Feb. 26, 1968 Patented Apr. 13, 1971 [54] PROGRESSIVE BURN SHELL 7 Claims, 14 Drawing Figs.

[52] US. Cl .1 102/42, 102/95 [51] Int. Cl F42b 7/02,

" F42b 7/08 Field ofSearch 102/42, 42 (C). 43. 43 (P).

[56] References Cited UNITED STATES PATENTS 3,088,405 5/1903 Clark, Jr 102/43 3,179,051 4/1965 Morse 102/42 (C) 3,289,586 12/1966 Horn et al. 102/42 3,401,588 9/1968 Olson 102/42 (C) 3,256,815 6/1966 Davidson et al. 102/42 3,283,720 11/1966 Foote et al l02/42(C) 3,352,239 11/1967 Schinnerer et a1 102/95X Primary Examiner-Robert F. Stahl Attorney-Bernard A. Reiter ABSTRACT: A shotgun shell designed to generate a lower and more extended pressure curve upon ignition of the powder. The shell consists of a conventional casing, primer and shot cup, the latter being made of any of a number of configurations and, materials. Disposed intermediate, the

primer end and in covering relation to the powder is a pressure plate that conforms to the cross-sectional shape of the casing interior. The pressure plate, in preferred form, contains a plurality of apertures so that upon application of a specified relatively low pressure, the surface area of the plate which the apertures define is caused to fracture, thus reducing the pressure in the powder chamber of the casing. As a result, the increasing kinetic energy generated by the continued burning of the powder (which is normally utilized to initiate movement of the static shop cup) may be applied toward the accelerationof the shop cup since the initial movement of the cup will have been initiated by the low-pressure force occurring upon fracturing of the plate.

Patented April 13, 1971 3, 13

2 Sheets-Sheet 1 mm FIG. 2Q

FIG. 5 52 CLIFFORD LOGAN ASHBROOK e 60 W/LSON GORDON W/NG INVEN'IURS 3 BY BERNARD A. RE/TER Patented April 13, 1971 2 Sheets-Sheet 2 T/ME (M/LL/SECONDS) C L/F F 0RD LOGAN ASHBROOAK W/LSON GORDON WING INVEN'IURS BY BERNARD 4. 95/759 ATTORNE V BACKGROUND OF THE INVENTION Shotshell wad desimrers have, in the past, sttived for wad columns which, in addition to scaling the powder gases behind the shot charge so as to obtain maximum velocity, have been light and compressible. Wad lightness permits the use of less propellant to obtain the same shot charge velocity and reduces the amount of recoil. compressibility is desirable to cushion the impact generated by the expanding powder gases so as to set the shot charge in motion more gradually and thereby reduce deformation. The pressure generated upon and during ignition of the powder is of cardinal importance in influencing the velocity of the shot projectiles. From a mechanical viewpoint this occurs simply upon receipt of a flash from the primer, whereupon, the powder is promptly, in a matter of a few thousandths of a second, converted into gases having a volume of magnitude many times that of the original powder .vo'lume. Since the pressure increases almost instantaneously,

the shot is substantially exploded down the barrel, but due to the expanding volumetric area for the gases behind the shot,

" the gas pressure very quicldy deteriorates or drops off. It will be recognized that the rapid buildup in pressure, to be effective in propelling the shot at the greatest velocity, should be maintained or if possible increased as long as the shot is in the bore. To accomplish this end the shotgun shell industry has heretofore utilized an element or wad within the shell casing. The wad has commonly been inserted over the powder and forced down thereon with a given pressure so as to insure a tight seal. In so doing, however, the filler wad (in cases where a double wadding is used) is often so compressed that the cushioning" effect of the wad column is substantially lost. Despite such factors as the well-known progressive burn powders which are available on the market, the pressure builds up almost instantaneously and the wad in conventional shells requires a substantial force before it is moved by the expanding gases, and the pressure peak is reached or even passed before the wad and shot have moved a fraction of the bore distance. As a result, a very good portion of the pressure is utilized in overcoming the static state of the wad and the shot cup, and one of the primary objectives of the entire structure, that is, high shot velocity, is materially reduced since the pressure remaining in the powder chamber is being reduced as the shot traverses the bore. This in combination with frictional resistance of the bore wall on the shot cup realistically reduce the potential velocity obtainable from a given powder charge.

DESCRIPTION OF THE INVENTION The present invention is directed to an improved shell construction in which the pressure curve of the ignited powder can be mechanically controlled so as to markedly enhance muzzle velocities of the departing shot, by as much or more than 50 percent over velocities presently obtained. In addition thereto, the invention discloses genuine and unique contribution to the advancement of the art in the form of a shotgun shell in which the wadding, as it has heretofore been known, is eliminated in favor of a simple plate. This pressure plate, as it may be referred to, need not be posin'oned under pressure as is commonly done with wads and is so designed as to provide for predetermined control of the shells internal pressure on a time basis. A further advantage of the invention resides in the increased kinetic energy, range and penetration of the shot, all of which inherently flow from higher muzzle velocities. A still further advantage resides in the improved shot pattern made possible by the markedly increased velocities, this being due to elimination of air turbulence at muzzle velocities well above the speed of sound. Still further, due to the higher kinetic energy per shot pellet, there is required a lesser number of pellets per cartridge shell to maintain fire power. As a consequence a shorter shell may be constructed thus resulting in lower manufacturing costs. Conversely more pellets could be placed in a conventional shell to thereby These and numerous other features and advantages of the invention will become apparent upon careful reading of the following detailed description, claims, and drawings, wherein like numerals denote like parts in the several views and wherein:

FIG. 1 is a longitudinal sectional view of a preferred form of the invention.

FIG. 2 illustrates a plan view of the pressure plate in FIG. 1.

FIG. 2a is a sectional view along the plane A-A of FIG. 2.

FIG. 3 is a plan view of an alternate pressure plate.

FIG. 3a) is a sectional view along the plane A-A of FIG. 3.

FIG. 4 is a plan view of another alternate pressure plate.

FIG. 4a is a sectional view along the plane A-A of FIG. 4.

FIG. 5 is a plan view of still another alternate pressure plate.

FIG. 5a is a sectional view along the plane A-A of FIG. 5.

FIG. 6 shows an alternate means for mounting the pressure plate.

FIG. 7 shows another alternate means for mounting the pressure plate.

FIG. 8 shows still another form of the invention.

FIG. 9 illustrates graphically pressure time and movement performance curves of a conventional shell as compared to a shotgun shell constructed in accordance with the invention.

FIG. 10 illustrates a modified form of the invention wherein the pressure plate is of nonfracturing material.

With reference to FIG. 1 there is shown a shotgun shell or cartridge having a cylindrical casing 2 with base end 4 and crimp end 6. The base end has an axially disposed circular aperture 7 for receiving a conventional primer 8 therein. The interior of the cartridge is characterized by shelf 10 which defines the upper perimeter of powder charge cavity 12. The powder charge cavity is further defined by the internal cylindrical wall 14 of the cartridge, by annular base wall 16, and by the frustopyrarnidal wall 18, containing the primer aperture 7. In the present device there is utilized, instead of the conventional wadding arrangements, a pressure plate 22 which may be made of various materials such as a plastic or metal. The material of the plate 22 will depend upon the material of the cartridge or casing 2 itself. It may also depend upon the method of attachment to the casing. If the casing is made of polycarbonate plastic, as is common, the plate may be made of acrylic plastic and should be seated on shelf 10 after the powder is poured into the cavity. The plate would be welded to the casing internal wall by means of a methylene chloride seal 26 (shown in exaggerated form) or it may be adhesively connected. Similarly, if the casing were another material, such as paper or metal, the plate could be emplaced by crimping of the casing wall above the plate. Means other than a shelf for mounting the pressure plate are described hereinafter. In any event it should be noted that the tensile strength of the material from which the pressure plate 22 is constructed should be of a lower magnitude than that of the casing itself, for it is a primary purpose of the plate to fracture after the pressure in cavity 12 has achieved some predetermined level. The means of attachment of the plate to the wall must likewise be such that, when the pressure reaches a specified level, the plate will sever from the casing internal wall entirely. It will be readily recognized that the fracturing and the severance could occur simultaneously or individually without the occurrence of the other at all, if same were so desired. Disposed above the pressure plate 22 and in normally contacting relation thereto, is a shot cup 30 which, for exemplary purposes, may take the form as illustrated wherein there is provided the shot receiving portion 32 having slide flange 34 for preventing gas blowby.

The aforementioned pressure plate 22 may take any of a number of forms. A common characteristics of all except one of the exemplary forms is the ability to fracture away a portion of the plate at some predetermined pressure. The purpose of this is, as previously explained, to increase the volumetric displacement of the gas pressure in powder cavity 12, thereby reducing the time rate of increase of the pressure. By accomplishing this, the pressure in cavity 12 will be increasing rather than decreasing as the shell traverses the bore, thus enhancing acceleration.

As shown in FIG. 9 the time rate of change of pressure in the powder cavity is extremely fast, there occurring a peak pressure in less than 2 milliseconds. As soon as the powder begins to burn the pressure increase is initiated, until there is sufficient pressure to cause the shot cup to start to move. Even with common slow burning smokeless powders this occurs in a fraction of a second, since the burning is an exothermic reaction in which the heat given off during the powders change from a solid to gaseous state causes rapid increase in pressure. The rate of increase in a conventional wad-type cartridge is illustrated by the line (A) wherein it may be seen that peak pressure is reached long before maximum velocity (see velocity line B) of the shot cup is achieved. The ramification of this measurement is apparent when it is recognized that as the cup begins to accelerate the pressure begins to decline due to the volumetric increase between the base wall 16 and the rear of the moving wad. The peak pressure therefore is, in a conventional shell, utilized in great measure in overcoming the frictional force of the cup against the cartridge wall, and the force which actually accelerates the cup from the cartridge is clearly not the peak pressure but instead the downhill pressure created by the expanding volume. As a consequence of this, the total energy available for enhancing muzzle velocity is normally partially lost. By utilization of the pressure plate structure, the pressure curve of the same gun powder is managed so as to optimize the pressures affect on the velocity of the shot. This is done by providing in the plate 22 a plurality of holes, as for example at 40, 42, 44, 46, 48, 50 (FIG. 2, 2a) which are disposed to define a first triangular breakaway area delineated by the dotted lines between the holes 42, 46 and 50. These holes are so spaced with respect to each other that fracturing of the area defined by the dotted lines between them is calculated to occur at a predetermined chamber pressure of approximately 500 p.s.i. At that time no movement of the shot cup occurs, except that the opposing forces of friction between the cup and cartridge wall is being approached by the pressure buildup in the powder cavity. At the predetermined pressure, fracture of "the plate area defined by holes 42, 46 and 50 occurs, resulting in a volumetric increase of the cavity 12 wherein is contained the rapidly expanding gases. The increase of volume of course reduces the rate of increase, thus shifting the pressure curve over slightly. This first fracture is illustrated at point (1), FIG. 9. Shortly thereafter (one-ten thousandth of a second) the expanding gases create a sufficient pressure to fracture the larger area of the pressure plate defined by the holes 40, 44 and 48. At approximately this moment everything forward of the plate 22 begins to move, i.e., shot cup and shot. It is noted, however, that maximum pressure has not yet been achieved (see point (2), FIG. 9). It may be pointed out that the pressure plate may include only a single fracture area rather than two so that there will be, in the course of the pressure buildup, a single reduction in the acceleration of the pressure curve. It will similarly be recognized that the pressure plate could take any number of forms which would provide for reduction of the pressure acceleration subsequent to ignition. In either event, the plate will shortly after, sever from the wall 14 itself (point 3) thus shifting the curve further to delay the point of maximum pressure buildup. In this way the shot cup 30 has begun substantial movement down the shell wall prior to the point of maximum pressure buildup, thereby permitting the maximum pressure to subsequently accelerate the cup.

Among the many different forms of pressure plates which may be used in this manner are those illustrated in FIGS. 3 and 5. In FIG. 3, for example, is shown a pressure plate 22 having a plurality of apertures defining to concentric rings 50, 52. The apertures of inner ring 50 are spaced at a predetermined linear distance (d) from each other so that the sum of the linear distance totals 5 inchesa' inches. Depending upon the type of plate material, the thickness of plate material, and the plate area encompassed by the holes, the force required to fracture the plate may be easily calculated. Conversely, if the force (say 540 p.s.i.) which is intended to fracture the plate is known, then the plate can readily be designed to fracture at or near that force level. Disposed exteriorly to ring 50 is the ring of apertures 52 which, in the same manner as the plate of FIG. 2, is adapted to fracture subsequent to the inner ring but at a higher pressure level, say 825 p.s.i. The aperture distances may likewise be calculated to fracture at a predetermined pressure.

A still further modification of the disc is exemplified by FIGS. 4, 4a where the first fracture area is defined by an inner notch 56 which is somewhat deeper (FIG. 40) that the outer notch 58 defining the second fracture area. The size and shape of the notches may clearly vary, and the same may easily be calculated in accordance with factors such as the plate material, the relative areas of fracture and the material of the plate. In FIG. 5, 5a is illustrated still another form of pressure plate 22 in which the fracture areas are defined by stepped recesses 60, 62 having respective areas that may be calculated in accordance with above described principles corresponding to a predetermined fracture pressure.

Another form of pressure plate is shown in FIG. 10 wherein the plate does not contain fracture areas but instead is adapted to expand upon the application of pressure F. Expansion causes an increase in volume, thus reducing the rate of pressure increase. At a predetermined level of pressure the plate will slip from beneath shoulder 10 and be propelled out of the bore. It may be recognized that accomplishment of this result may require a variance in the plate thickness, with the center of the plate being thinner than the remainder.

The pressure plate of the invention may be mounted in any number of ways. Several mounting means are illustrated in FIGS. 6-8. In FIG. 6, for example, is shown a cartridge body of laminated paper in which the internal layer is inwardly lodged to form a flange 64. The plate 22 may then be affixed to the flange by adhesive or other appropriate means. In FIG. 7 is shown another manner for mounting a plate. Here, after the plate is placed over the powder, an annular ring 68 may be set on top of the plate and afixed to the sidewall of the cartridge. Further, as shown in FIG. 8, the concept of the plate could take the form of a unitary structure or cup 70 which contains the powder and whose top wall 22 constitutes the pressure plate itself. The legs of the cup could be adapted then to fracture at the desired pressure.

In operation, the improved cartridge of the invention presents several distinctly advantageous features. The most pronounced of these, as explained hereinabove, is the markedly improve muzzle velocity and hence kinetic energy of the shot. For example, muzzle velocities commonly obtained heretofore have been in the range of l,200-l,300 ft./sec. The kinetic energy in one pellet or shot achieved at 1,250 ft./sec. may be described as:

where one (1) pellet Weighs 20 grains and 7,000 grains =1 pound. (#4 buckshot).

(3) K.E'.=69,537 ft. lbs/sec.

This may be compared with the improved velocity cartridge of the invention wherein:

(2) K.E.=l44,l92 ft. lbs/sec.

Thus, the pronounced increase in velocity of the shot, caused by pressure plate management of the pressures so as to apply peak cartridge pressure toward acceleration of the shot rather than overcoming shot cup friction, provides for substantially twice the kinetic energy per pellet than was previously available. As shown in H6. 9, alter the second fracture of the plate occurs, the pressure still continues to climb. At this point (i.e., 2nd fracture), or within several microseconds thereafter, the shot cup will begin to move forward, thus causing a continuous volumetric change within the powder chamber. Since the powder burn rate exceeds the volumetric rate of change the pressure will for a short time continue to climb. The cartridge movement at this point is reaching its maximum within the gun barrel. As illustrated, the pressure in a conventional cartridge has peaked out by this time and is rapidly deteriorating and thus there is little, if any, force acting to accelerate the shot cup. In the improved cartridge the pressure increases during and after initial shot cup movement, thus accelerating the shot; the pressure moreover continues at a higher level than was possible heretofore, thereby further contributing to the acceleration. Thus, it is possible to obtain velocities substantially well above those presently obtainable. in many tests velocities of over 50 percent higher than conventional present day shells have been achieved, all without excessive chamber pressures.

It should be understood that changes an modifications in the formation, construction, arrangement and combination of the cartridge of the invention may be made and substituted without departing from the spirit and principles of the invention and that the modifications shown herein are only representative of the innumerable forms of the invention.

We claim:

1. In combination, a shotshell comprising a cylindrical casing having a primer and and a shot ejecting end, a powder cavity adjacent said primer end and a shot cup disposed within said shotshell in overlying relation to said powder cavity, the improvement consisting of:

partition means separating said powder cavity from said shot cup and disposed in abutting relation to the internal wall of said shotshell, said partition means adapted to be projected towards said shot ejecting end subsequent to the ignition of the powder in said powder cavity and upon the buildup of a predetermined pressure level therein, the partition means thus 'acting as a pressure plate, said pressure plate being characterized by means thereon defining distinct surface areas of predetermined size, each said means adapted to cause fracturing of the area defined thereby at its respective pressure point, thus delaying the rate of pressure buildup in said powder cavity.

2. The combination as recited in claim 1 wherein the ultimate tensile strength of said partition means is lower than the walls of said cylindrical casing.

3. The combination as recited in claim 1 wherein the partition means on said pressure plate are of different thicknesses so as to thereby enhance the fracturing at said predetermined pressure levels.

4. The combination of claim 1 wherein said partition means is fixedly connected to said internal wall by flange means, said flange means being integral with said internal wall and disposed in abutting relation to the surface of the pressure plate adjacent said shot cup.

5. The combination as recited in claim 1 wherein the said partition means is adapted to fracture initially at its central area and subsequently in areas immediately adjacent to the central area.

6. A shotshell comprising a cylindrical casing, a shot cup within said casing, a powder cavity having loosely placed powder therein within said cavity at an end thereof opposite said shot cup, and the improvements consisting of: a pressure plate having areas of varying tensile strength, said pressure plate being fixedly disposed intermediate said shot cup and said powder cavity said pressure plate being characterized by means thereon defining distinct surface areas of varying size,

said areas being adapted to selectively fracture from said plate thereby releasing gases of expansion within the powder chamber and delaying in time the point of maximum pressure buildup therein.

7. The shotshell of claim 6 wherein said areas of varying tensile strength are defined by channels of reduced thickness in said pressure plate, the thickness of said channels being related to the relative level of pressure at which the plate is to fracture. 

1. In combination, a shotshelL comprising a cylindrical casing having a primer end and a shot ejecting end, a powder cavity adjacent said primer end and a shot cup disposed within said shotshell in overlying relation to said powder cavity, the improvement consisting of: partition means separating said powder cavity from said shot cup and disposed in abutting relation to the internal wall of said shotshell, said partition means adapted to be projected towards said shot ejecting end subsequent to the ignition of the powder in said powder cavity and upon the buildup of a predetermined pressure level therein, the partition means thus acting as a pressure plate, said pressure plate being characterized by means thereon defining distinct surface areas of predetermined size, each said means adapted to cause fracturing of the area defined thereby at its respective pressure point, thus delaying the rate of pressure buildup in said powder cavity.
 2. The combination as recited in claim 1 wherein the ultimate tensile strength of said partition means is lower than the walls of said cylindrical casing.
 3. The combination as recited in claim 1 wherein the partition means on said pressure plate are of different thicknesses so as to thereby enhance the fracturing at said predetermined pressure levels.
 4. The combination of claim 1 wherein said partition means is fixedly connected to said internal wall by flange means, said flange means being integral with said internal wall and disposed in abutting relation to the surface of the pressure plate adjacent said shot cup.
 5. The combination as recited in claim 1 wherein the said partition means is adapted to fracture initially at its central area and subsequently in areas immediately adjacent to the central area.
 6. A shotshell comprising a cylindrical casing, a shot cup within said casing, a powder cavity having loosely placed powder therein within said cavity at an end thereof opposite said shot cup, and the improvements consisting of: a pressure plate having areas of varying tensile strength, said pressure plate being fixedly disposed intermediate said shot cup and said powder cavity, said pressure plate being characterized by means thereon defining distinct surface areas of varying size, said areas being adapted to selectively fracture from said plate thereby releasing gases of expansion within the powder chamber and delaying in time the point of maximum pressure buildup therein.
 7. The shotshell of claim 6 wherein said areas of varying tensile strength are defined by channels of reduced thickness in said pressure plate, the thickness of said channels being related to the relative level of pressure at which the plate is to fracture. 